Update output to be compatible with Jenkins JUnit

Fixes #8

Validated output against XSD at https://svn.jenkins-ci.org/trunk/hudson/dtkit/dtkit-format/dtkit-junit-model/src/main/resources/com/thalesgroup/dtkit/junit/model/xsd/junit-7.xsd using http://www.utilities-online.info/xsdvalidation/
Merge pull request #1 from brycekahle/patch-1

Update output to be compatible with Jenkins JUnit